The present invention relates to a method of and an arrangement for producing pressed shaped bodies of a non-swelling mixture of fibrous materials mixed with a heat-hardenable binding agent.
Methods and arrangements of the abovementioned general type are known in the art. The mixture is pre-pressed (rough pressed) and subsequently hardened in a hot press to its final shape. A first lower part of a pressing tool is placed into a press and is pressed there by closing of the press with simultaneous pre-pressing in an upper part of the pressing tool. Then instead of the first lower part of the pressing tool, a second lower part of the pressing tool is placed. Such a method and an arrangement are disclosed, for example, in the German Pat. No. 2,309,975 which corresponds to the U.S. Pat. Nos. 3,975,127 and 3,997,643. The non-swelling mixture is composed frequently of ligno-cellulose containing fiber materials such as comminuted and dried wood chips, bagasse fibers, etc., mixed with a heat-hardenable synthetic resin such as melamine resin, urea formaldehyde resin or phenol formaldehyde resin. Instead of the comminuted and dried wooden or bagasse fibers, fibers of other materials can be used such as glass fibers, stone wool, alone or in a mixture with one another, with admixture of respective advantageously organic binding agent.
The novel methods and the respective arrangements for performing the methods are provided for producing of relatively small shaped bodies, such as for example discs with a diameter of 5 cm, or grid-like lattice elements composed of rings and connecting webs with small wall thickness such as for example ornamental grate or coloring grate elements. The known methods are also successful for production of these products when their components have a uniform thickness. However, the known methods lead to qualitatively not satisfying products when the components of the products to be produced, for example, a covering grate element have webs which are offset in stepped manner, for example having different depths. When these products are produced in accordance with known methods, a seam can form at their side which is provided with webs of different depths and which simultaneously is a visible side of the product. Removal of the seam is very expensive or not possible at all.